I am working on bringing files into Lightroom 4, most DNG files from a Canon 5D and DNG and TIFF files from a Nikon scanner. The problem I'm having is that after importing the files into the Folder in which they will all be for the catalogue, they are significantly smaller. For instance, a DNG file from a 6x9 film scan is 600MB in the original folder, then is 420MB in the new folder after being renamed and imported into Lightoom. Similarly, a 20MB DNG file from my Canon 5D is 8MB after importantion. Also, the backup of the original that is made upon importantion, remains at its larger size on my external drive. I do not believe that I have anything set in Lightroom to do this, the only setting I've touched in the import process are renaming the file, placing a backup, and adding tags. I am not doing anything in the development dialogue box. Is there a reason that these files are so much smaller? I'm worried because 30% decline in the case of scans is a lot of data, as if the 70% decline in my Canon 5D file. Any ideas?

There are two things going on....(1) one is yes, my raw Canon files are being converted to DNG files. I think that is ok. The files are smaller, but that is because DNG has some form of nonossy compression, right? Are there other options in Lightroom? I guess I can go through ACR in batch and choose other options, but I cannot see other options in Lightroom. (2) I have some legacy scans from Vuescan that are already in DNG. What I've found is that, becauseI was selecting "copy as DNG" on an already existing DNG file, the file was then being made MUCH smaller. I'm not sure why, or if it matters, but I decided to change the process to simply move the DNG files, rather than copy them, and the sizes are remaining the same. Thoughts?

In the Import menu you can choose to leave the files in your native camera format. In the top center of the screen are your choices. I won't convert unless I need the additional disk space or Nikon and Cannon agree to use that format (how about never?)

No. In the import menu just choose "Copy" on the top line and "Copy to new location and add to catalog" on the line below before you select "Import" and your CR2s will show up where you want them without further processing. You can covert them later to DNG from within LR if you want that format. Remember to also choose the file names, folder and drive location you want on import as well.